The Discovery of Quasicrystals: The 2011 Nobel Prize in Chemistry

Listen to the announcement of the 2011 Nobel Prize in Chemistry, to Daniel Shechtman of the Technion-Israel Institute of Technology. Then hear comments from the president of the American Chemical Society, Nancy Jackson, of Sandia National Laboratories

Steve: Steve Mirsky here with another special Nobel edition of the Scientific American podcast, Science Talk, posted on October 5th, 2011. Early this morning on the clock here in New York City, the Royal Swedish Academy of Sciences awarded the Nobel Prize in Chemistry. What follows is an edit of the announcement and press conference. The first voice you hear is the academy's Staffan Normark.

Normark: This year's prize was a remarkable mosaic of atoms. The Royal Swedish Academy of Sciences has decided to award the 2011 Nobel Prize in Chemistry to Professor Daniel Shechtman at Technion Israeli Institute of Technology, Haifa, Israel and the academy citation runs: "For the discovery of quasi crystals." Professor Lars Thelander will now give us the short summary in English, please.

Thelander: I will give a brief introduction to the prize and hand over to Professor Lidin for a more detailed description. This year's Nobel Prize in chemistry awards one scientist, Daniel Shechtman. His discovery of quasicrystals revealed a new principal for packing of atoms and molecules in solid material. This led to a paradigm shift within chemistry. It also stimulated two intense studies of the properties caused by the very special atomic packing. In quasicrystals, atoms pack in a regular manner. They follow mathematical rules and are highly ordered. But the pattern among the atoms is not repeating itself, like in some of the artistic medieval Islamic mosaics. Using transmission electron microscopy, Shechtman made the first experimental observation in 1982. He then recorded a tenfold atomic symmetry in a synthetic alloy of alumina and manganese. A tenfold symmetry within atoms was simply not allowed, according to the science of the time. It was considered against the laws of nature. Shechtman's results were therefore met with a high level of criticism, and there was a big controversy within the scientific community. Thanks to the very high quality of Shechtman's experimental data, the controversy was eventually settled and the paradigm shift occurred. Before Shechtman, crystals were considered to be made out of atoms packed in regularly ordered, repeating three-dimensional patterns. Today we know that those patterns do not have to repeat themselves, and I'll now hand over to Sven Lidin for a more detailed description.

Lidin: Quasicrystals is, in fact, a new field of cross disciplinary science drawing from and enriching chemistry, physics, mathematics and material science. Many people have contributed to the area of quasicrystals, but the discovery is down to one person alone; and only through skill, luck and good old-fashioned tenacity, was he able to convince a very, very skeptical world about the veracity of his findings. But let's first return to the original experiment. What Daniel Shechtman did was to submit a sample of aluminum-manganese alloy to an electron beam, causing the electron beam to diffract and giving rise to a pattern. Now this diffraction pattern, as it's called, shows us two things. First of all, it shows that the material is highly ordered, even at long scales. At the same time, if you look at the strong diffraction peaks, the bright spots, you can count them in rings around the central spot and there are always 10 of them, showing us we have tenfold symmetry. This is absolutely incompatible with what science tells us, and I will return to that. When Shechtman made this discovery, he also drew a picture of it, and he made a note, in the parentheses—tenfold???, with three question marks—because he was fully aware of the fact that this was indeed a symmetry forbidden for crystallographic objects. Something else which is very interesting, is the fact that we can date this discovery perfectly. Often the Nobel Prize is awarded to something that has developed over a long time. For this particular discovery, we know it took place on April the 8th, 1982. To understand why this is so remarkable, we have to look at the structure of normal materials. In all ordered materials, if we look closer, we will find that it's composed of crystals, and each of these crystals is composed by an ordered array of atoms, and it's a repeating array. This has been the paradigm for crystallinity and for order in the solid state ever since the beginning of last century. Only certain symmetries are allowed to be present in a periodically repeating pattern. In fact, these symmetries generate the repeating pattern. They have been found in many different systems apart from the original metallic systems. We now have them in micellar systems, in liquid crystals, in polymer systems and so on. And just last year, a mineral was found in the Khatryka River in eastern Russia, which has this symmetry—not the river, the mineral—and the mineral is today called Icosahedrite. Unique materials have unique properties and are therefore also useful. I would stress that the discovery of quasicrystals, the most important thing about the quasicrystals are their meaning for fundamental science. They have rewritten the first chapter in the textbooks of ordered matter. But we also find them in useful objects. In this case, we see Icosahedral quasicrystals as a strengthening phase in a Swedish high-quality steel. They have also been used in experiments to strengthen turbine blades and in thermoelectric applications, that is trying to convert heat gradient directly into electricity. All these applications come out of the specific properties of quasicrystals, that they are poor conductors of heat, they have very low-energy surfaces, they have low friction and they have low adhesion properties. The discovery of quasicrystals, as I said, is down to Daniel Shechtman. The discovery was made, while he was on a sabbatical at National Bureau of Standards, which today is the NIST, the National Institute of Science and Technology in the United States. But Daniel Shechtman himself is based in Haifa in Israel. The quasicrystals that he has discovered has enriched many fields of science, and today you find that sort of pattern occurring in many places, even in the logotype of this academy.

Normark: Thank you Professor Lidin. You should say that Professor Shechtman is 70 years old. It's one of the first times we can date the discovery to one single day, but we don't know if it was morning or evening—do we know?

Lidin: I think according to an interview that I've had with Professor Shechtman that it was actually in the morning. (laughter) He found this image in his microscope. He rushed out into the corridors outside, but being the early morning hours, when the microscope was readily available, there was no one else there.

Normark: He's not on the line; perhaps we can take some questions to the podium here; we have some experts. Do we have some questions?

Questioner: There are several mathematicians, who have contributed to this field, like Roger Penrose, and, I think, just a couple of years ago, there was some description. You choose not to include them—why?

Lidin: This Nobel Prize is given to Daniel Shechtman for the discovery of quasicrystals and that is the discovery of this behavior in actual chemical-physical system. There have been mathematical models around for a very long time. And there have certainly been great contributions of the mathematicians involved, but it is a very long story dating back to very early days. The choice of awarding the chemical discovery and the chemical discovery is due to Daniel Shechtman and Daniel Shechtman alone. But as I started out, there have been many very interesting contributions in this field, in very many different areas. But the person who started it all was Daniel Shechtman alone.

Normark: Do we have some more questions? I can assure you, we have talked to him and he was excited about getting this prize, and he said that he had perhaps dreamt about it but had given up the hope to get it. So I think it came as a surprise. Perhaps, Professor Lidin can say what are the different states in the science that came after this particular discovery?

Lidin: Absolutely. First of all, the discovery took a long time to filter through the academic system. It's a very important discovery on the sole basis that it shakes the foundations of solid state sciences, the fact that it is quite contrary to what we knew before. In fact, it has even left us knowing less than we did before the discovery. It has changed the concept of crystallinity in such a way that we, before the discovery of Daniel Shechtman, there was a definition of crystallinity that dealt with the order found within a crystal. The new definition of crystallinity doesn't attempt to define this, because we simply know that we do not know what constitutes a crystal. Instead the definition is that anything that gives a well-defined diffraction pattern is a crystal. So it's an operative definition, leaving very open for new discoveries. It took a long time even within the very small world of intermetallic chemistry for this discovery to be completely accepted. And it's only after, it is only in the last six, seven years, that we have seen quasicrystals in other fields of science outside of intermetallics. And it was only in 2007 that for the first time, we got a truly highly resolved crystal structure of quasicrystals so that today we know exactly where the atoms are. It has been a gradual development, our understanding has slowly emerged of what a quasicrystal is. And today we can say with complete confidence that we know what quasicrystals are, why they are and how they are and thus the time was right for a prize.

Steve: Later in the morning, I got comments from Nancy Jackson, she's the current president of the American Chemical Society. She's also the manager of the International Chemical Threat Reduction Department at Sandia National Labs. I called her in New Mexico.

Jackson: It's one of these great stories in science, where a scientist thought that what he discovered and was suggesting could not exist. And my understanding is that one of the people who told him that his claims were impossible was Nobel Prize­–winning Linus Pauling himself.

Steve: That's a really interesting wrinkle in the story.

Jackson: (laughter) So, you can imagine how it must have been for him. You know, this was quite a while ago. This was 30 years ago, so he would have been, what, in his 40s and that takes a lot of self-conviction. So that's very impressive. And he stuck to his guns, because the evidence showed one thing: new materials have new properties. Though I suspect we will continue to find even more applications for these kinds of materials.

Steve: What are some of the applications that have already been discovered for quasicrystals?

Jackson: Well, one thing that they are used in is in making a certain kind of steel. So, basically what they do is they put small particles of quasicrystal—you know, like putting fruits in Jell-O and the Jell-O is a softer form of steel and quasicrystals are like the fruit (laughter) in the Jell-O—and that makes really resilient steel; very strong, sort of, resilient, so it can, you know, take pressure without breaking and all that sort of thing. And, in fact, one of the things they use them for is needles in surgery, particularly in eye surgery, where you have to be perfect. You know you have no room for error, and so you want your needle to do exactly—this really hard needle—to do exactly what you want it to do.

Steve: Well, that's really interesting. Let me also point out, you know, it might sound funny to people you used the fruit in the Jell-O analogy, but science has a long and storied history, going back to Rutherford's plum-pudding model of the atom. So we've been doing this for a long time, where we take fruit and put it in something else and then use that as an analogy for what's going on in on the microscopic scale. (laughter)

Jackson: Yes. It's helpful for understanding.

Steve: Any other applications that come to mind for quasicrystals?

Jackson: Yeah, one of the unique properties of this crystal—and I guess, you know, it kind of makes sense—is that it does not transfer heat well or electricity, which is somewhat unusual for a crystal, but I guess, because of its lack of periodicity. So one thing we're looking at is putting it on an aluminum pan that you might cook with; and what that does is—yes, it has some nonstick properties and that's nice—but what it does is that it doesn't transfer the heat as well, which actually means that you can cook things without burning them, you can cook them at a good temperature. You know, just like sometimes, we add a little water to something we're cooking so that it doesn't overheat, you can have this sort of trait, it will help you in cooking things more evenly without burning things and that sort of thing. That's an interesting, sort of, maybe not groundbreaking, but it's an interesting idea. And the other thing too, is that they're used as thermoelectric devices, which means that they turn heat into electricity, which could have wonderful implications in the energy world because one of the things that we have in our manufacturing processes and in our electronic equipment is a lot of heat, you know, waste heat. And, boy, that would be big to be able to use it for electricity.

Steve: And why don't we talk just a little bit about the fundamental nature of this discovery, how it really, kind of, rewrote the textbooks.

Jackson: Yes. That's what makes it so exciting, that's what makes it, I mean, there's nothing more exciting for a scientist than to have strong evidence that changes a paradigm in understanding. And that's what his work did—the understanding of how crystals were made, what crystals were and about the understanding of symmetry, had to be completely rethought and redone after they accepted that what he found was real.

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